1. Field of the Invention
The present invention relates to an electro mechanical device and a manufacturing method thereof, and to a resonator and a manufacturing method thereof.
2. Description of the Related Art
In recent years, along with the progress of miniaturizing manufacture technique on a substrate, an electro mechanical device, a so-called micro-machine (ultra-small electrical/mechanical composite device: Micro Electro Mechanical Systems, hereinafter, referred to as MEMS) and a small device assembled with the MEMS device thereof have received a remarkable attention. The MEMS device is a device wherein a vibrator which is a movable structure body, a semiconductor integrated circuit controlling the drive of the vibrator and the like are coupled electrically/mechanically. Then, the vibrator is assembled into a portion of the device and it is constituted such that the drive of the vibrator is to be carried out electrically by applying Coulomb attraction or the like between the electrodes.
Among such MEMS devices, in particular, a device formed by using a semiconductor process has features in which a small area is occupied by the device, a high Q value (quantity indicating resonance acuteness of vibration system) can be realized, it can be integrated (unified) with another semiconductor device and the like, so that utilization as a high frequency filter for wireless communication was proposed (for example, see Patent Document 1).
Incidentally, in a case wherein the MEMS device is integrated with another semiconductor device, there was proposed a way in which the vibrator portion in the MEMS device is capsule-sealed and thereby arrangement of wiring or the like is made to be possible in further upper layer (for example, see Page 7 and Page 10 of Japanese Unexamined Patent Publication No. 2002-94328 of Patent Document 1). However, when capsule-sealing the vibrator, it is necessary to keep a space at the periphery of the variable portion of the vibrator and to make a state in which the vibrator is to be movable. The space keeping at the periphery of this variable portion is usually carried out by so-called sacrifice layer etching (see C. T.-C. Nguyen, “Micromechanical components for miniaturized low-power communications (invited plenary)”, proceedings, 1999 IEEE MTT-S International Microwave Symposium RFMEMS Workshop, Jun. 18, 1999, pp. 48-77 of Non-patent Document 2).
The sacrifice layer etching means an etching in which a thin film is formed at the periphery of the variable portion of the vibrator beforehand and thereafter, this thin film is removed by etching and a space (gap) is formed at the periphery of aforesaid variable portion. Also, the thin film formed at the periphery of the variable portion in order to carry out the etching of the sacrifice layer is called a “sacrifice layer”.
The research and development of the MEMS device has been developed in various kinds of fields such as various kinds of sensors, actuators, optical devices, other MEMS devices and the like other than the high frequency filter.